Re: Prayer time adjustment in Toronto
This is one of a number of fiqh rulings on Isha when the phenomenon of "persisting twilight" occurs.
Persisting twilight is when the event of Isha doesn't occur i.e the evening joins on to the dawn without going in to night.
Earlier there were attempts to reclassify when Isha occurs ... there is a difference of opinion;
Shafq-al-ahmar and Shafq-al-abyad (Red Set and White set)
According to measurements Red set occurs when the sun is 15 degrees below the horizon, white set is when the sun is 18 (more accurately 17.6 degrees below)
True isha occurs when the light from the sun cannot be seen. This happens at astronomical twilight which is around 18 degrees declination.
Some people asked is it possible to miss the isha prayer, on the basis that if we don't have a left hand and we do wudu, by not 'washing the left hand' will wudu be counted. This analogy was trumped with the better analogy regarding prayer which is based on the hadith of the dajjal. A time will come when a day will be so long etc etc, the sahabah (RA) asked about the prayers in their concern, the reply given by RasoolAllah (SAW) was you calculate.
So a few main methods of calculation were developed by Muslims scientists of the past. (hundreds of years ago)
Aqrab-al-balad - (nearest city)
nisf-ul-Lail - (half night)
Thulth-ul-lail - (3 split night)
Saba' al-lail - (7 split night)
Forgotten name - (Last observed time)
If there is a city that hits the shadow line of the sun at the same time as a candidate city then for that day (or for those few weeks) that city becomes the reference point. For the al-balad ruling. This is an ineffective method for very high latitudes.
the "lail" methods are where you take the point of sunset and sunrise and split the nights either in half, three or seven. First half, first third or first seventh is the isha threshold, and last half, last third or last seventh is the fajr threshold.
The last recorded time is the method that when the phenomenon was observable the last recorded time is kept every day until persisting twilight ends.
Mistakes in the calculation of Aqrab-al-balad can be made easily.
Other methods that would work fine are percentage/proportioned based on the pattern of prayer times of the nearest city ... which is an unofficial hybrid method.
The time difference of one city from it's maghrib to isha is the 'delta' take this 'delta' and add it to the maghrib of the candidate city and you get a form of calculated 'isha'.
Modernly with graphical tools they are using curve smoothing methods.